Bare rock is expos

ed

   

Lichens form Their acids break down rock into

particles These particles mix

with other dead lichens to form soil.

   

klk

After many years,

there is enough soil

Lichens are

replaced by

mosses Insects & other tiny organisms begin to live here.

Soil deepens Mosses are replaced by

ferns Ferns are replaced

by grasses & wildflowers

Small trees may grow if there is enough soil &

shrubs

Hundreds to thousands of years pass Soil can be deep and

stable enough to support a

forest.

Weeds such as crabgrass begins to

grow first.

   

New weeds such as horseweed appears due to seeds being spread by

wind or small insects.

Disturbance or natural disaster occurs causing severe damage to the

area. In this case, it is a fire.

In approximately 5 to 15 years, small conifer

trees may start growing among the weeds. The trees continue to grow. In about 100 years, a

forest may form

As older conifers die, they may be replaced by hardwoods, such as

oak or maple trees if the environment can

support them.

Crabgrass

Horseweed

Conifer Trees

Hardwoods(Oak or Maple)